1. Field of the Invention
The present invention relates to an optical instrument such as a telescope, a binoculars or the like, and more particularly to such an optical instrument for enabling the user to visually observe objects in a dark field which have small luminance that could not be perceived directly by the human eye.
2. Description of the Prior Art
It has been known to incorporate an image intensifier tube in an optical instrument such as a telescope or a binoculars for the purpose of enabling people to visually observe dark objects which could not be perceived directly by the human eye in darkness. However, such an optical instrument cannot be used in bright light since the image intensifier would be damaged by the intense light impinging thereon. The utility of the optical instrument is poor as it can only be used in the dark.